The Cysteine-Cysteine Family of Chemokines RANTES, MIP-1α, and MIP-1β Induce Trypanocidal Activity in Human Macrophages via Nitric Oxide

This paper describes a new role for the cysteine-cysteine (CC) chemokines RANTES, MIP-1alpha, and MIP-1beta on human macrophage function, which is the induction of nitric oxide (NO)-mediated trypanocidal activity. In a previous report, we showed that RANTES, MIP-1alpha and MIP-1beta enhance Trypanosoma cruzi uptake and promote parasite killing by human macrophages (M. F. Lima, Y. Zhang, and F. Villalta, Cell. Mol. Biol. 43:1067-1076, 1997). Here we study the mechanism by which RANTES, MIP-1alpha, and MIP-1beta activate human macrophages obtained from healthy individuals to kill T. cruzi. Treatment of human macrophages with different concentrations of RANTES, MIP-1alpha, and MIP-1beta enhances T. cruzi trypomastigote phagocytosis in a dose peak response. The optimal response induced by the three CC chemokines is attained at 500 ng/ml. The macrophage trypanocidal activity induced by CC chemokines can be completely inhibited by L-N-monomethyl arginine (L-NMMA), a specific inhibitor of the L-arginine:NO pathway, but not by its D-enantiomer. Culture supernatants of chemokine-treated human macrophages contain increased NO2- levels, and NO2- production is also specifically inhibited by L-NMMA. The amount of NO2- induced by these chemokines in human macrophages is comparable to the amount of NO2- induced by gamma interferon. The killing of trypomastigotes by NO in cell-free medium is blocked by an NO antagonist or a NO scavenger. This data supports the hypothesis that the CC chemokines RANTES, MIP-1alpha, and MIP-1beta activate human macrophages to kill T. cruzi via NO, which is an effective trypanocidal mechanism.